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Biomedical subjects

A Sener

Publications and source records attributed to A Sener.

At least 19 recordsLinked to original sources

Life satisfaction and leisure activities during men's retirement: a Turkish sample.

This study was planned and carried out as a pilot study to determine the life satisfaction of men from the Official Social Security Institutions in Turkey (n = 231). The Life Satisfaction Index was used as the measure. Among this group of retired men, the most popular leisure activities were audio-visual and reading. The strongest predictor of life satisfaction was the frequency of participation in leisure activities, followed by the level of satisfaction with health, income, and planning of leisure activities.

Aged↗

Alteration of adipocyte metabolism in omega3 fatty acid-depleted rats.

Presently an insufficient supply of long-chain polyunsaturated omega3 fatty acid is prevalent in Western populations leading to potential metabolic consequences. Based on this fact, this study deals mainly with various aspects of lipid metabolism in second generation female omega3-depleted rats. The parametrial fat and body weights were higher in omega3-depleted than control animals. This coincided with liver steatosis but did not alter heart triglyceride/phospholipid ratio. The net uptake of [U-14C] palmitate by adipocytes was also higher in omega3-depleted rats than in control animals. The uptake of D-[U- 4C] glucose or [1,2 (-14)C] acetate by adipocytes was lower, however in omega3-depleted than control animals and was unaffected by insulin in the former as distinct from latter animals. Despite comparable basal lipolysis, the increase in glycerol output from adipocytes provoked by theophylline was higher in omega3-depleted than control rats. The fatty acid pattern of lipids in adipose tissue was characterized in the omega3-depleted rats by a much lower omega3 content, higher apparent Delta 9-saturase and elongase activities, lower efficiency for the conversion of C18:2omega6 to C20:4omega6 and higher efficiency for the conversion of C18:3omega3 to C20:5omega3. These features were compared to those prevailing in liver and plasma lipids. The present study thus extends knowledge on the alteration of lipid metabolism resulting from a deficiency in long-chain polyunsaturated omega3 fatty acids.

Acetates↗

Pancreatic islet function in omega-3 fatty acid-depleted rats: alteration of calcium fluxes and calcium-dependent insulin release.

Considering the insufficient supply of long-chain polyunsaturated omega-3 fatty acids often prevailing in Western populations, this report deals mainly with alterations of Ca(2+) fluxes and Ca(2+)-dependent insulin secretory events in isolated pancreatic islets from omega-3-depleted rats. In terms of (45)Ca(2+) handling, the islets from omega-3-depleted rats, compared with those from normal animals, displayed an unaltered responsiveness to an increase in extracellular K(+) concentration, a lower inflow rate and lower fractional outflow rate of the divalent cation, and higher (45)Ca(2+)-labeled cellular pool(s) at isotopic equilibrium. The latter anomaly was corrected 120 min after intravenous injection of a novel medium-chain triglyceride-fish oil (MCT:FO) emulsion, distinct from a control omega-3-poor MCT-olive oil (MCT:OO) emulsion. At 8.3 mM D-glucose, insulin release was higher in islets from omega-3-depleted rats vs. control animals, coinciding with a higher cytosolic Ca(2+) concentration. The relative magnitude of the increase in insulin output attributable to a rise in D-glucose as well as extracellular Ca(2+) or K(+) concentration, to the absence vs. presence of verapamil and to the presence vs. absence of extracellular Ca(2+), theophylline, phorbol 12-myristate 13-acetate, or Ba(2+), was always more pronounced in islets from omega-3-depleted rats injected with the MCT:OO compared with the MCT:FO emulsion. A comparable situation prevailed when comparing islets from noninjected omega-3-depleted and normal rats. In light of these and previous findings, we propose that an impairment of Na(+),K(+)-ATPase activity plays a major, although not an exclusive, role in the perturbation of Ca(2+) fluxes and Ca(2+)-dependent secretory events in the islets from omega-3-depleted rats.

Animals↗

Rapid changes in liver lipid composition and pancreatic islet K+ handling and secretory behaviour provoked by the intravenous administration of a medium-chain triglyceride: fish oil emulsion to long-chain polyunsaturated omega3 fatty acid-depleted rats.

Second generation rats depleted in long-chain polyunsaturated omega3 fatty acids are currently used as an animal model for the insufficient dietary supply of such fatty acids often prevailing in Western populations. The present study deals mainly with the effects of a novel medium-chain triglyceride: fish oil emulsion (MCT:FO), as compared to a control medium-chain triglyceride:olive oil emulsion (MCT: OO), administered as an intravenous bolus to the omega3-depleted rats 60-120 min before sacrifice upon selected biochemical and biophysical variables. The major findings consisted of a severe decrease of the omega3 fatty acid content of liver lipids in non-injected omega3-depleted rats and its partial correction after injection of the MCT:FO emulsion. The omega3-depleted rats also displayed liver steatosis, increased incorporation of long-chain polyunsaturated omega6 fatty acids in liver phospholipids and increased activity of liver Delta9-desaturase. As judged from the effects of ouabain upon 86Rb net uptake by isolated pancreatic islets, the activity of Na+,K+-ATPase was virtually abolished in the omega3-depleted rats. The latter defect was corrected by prior intravenous injection of the MCT:FO emulsion, this coinciding with suppression of the excessive secretory response to a number of insulin secretagogues otherwise observed in the islets of omega3-depleted rats injected or not with the MCT:OO emulsion.

Animals↗

The effect of exercise on urinary gamma-glutamyl transferase and protein levels of volleyball players.

AIM: Postexercise proteinuria and increased urinary gamma-glutamyl transferase (GGT) levels can be indicative of exercise-induced renal damage. In the literature, there exists numerous studies on exercise-induced proteinuria; but studies investigating the effects of exercise on urinary GGT levels are quite few. We aimed to evaluate the effects of exercise on renal function, expressed through the exercise-induced differences in urinary GGT, creatinine and protein levels. METHODS: The study was performed on 12 female and 12 male volleyball players of the same sports club. Urine samples collected before and 1 h after the exercise were analyzed for urinary GGT, creatinine and protein amounts. RESULTS: No statistically significant difference was observed between pre- and postexercise urinary GGT levels (U/L and U/g creatinine) of female and male volleyball players (P>0.05). A significant exercise-induced increase in urinary protein excretion was observed for the male players, while a significant exercise-induced increase in urinary creatinine excretion was observed for the female players (P<0.05). When urinary GGT levels (U/L) were compared separately for setters and spikers, it was observed that female players had no significant difference, while male spikers had a statistically significant exercise-induced increase in the urinary GGT levels (U/L) (P<0.05). CONCLUSIONS: We suggest that the insignificance of the exercise-induced increases in the urinary parameters could be due to the relatively short-course of the exercise and the timing of postexercise urine collection. A comprehensive study performed on more subjects could yield results that are more significant.

Adolescent↗

Changes in NAD/ADP-ribose metabolism in rectal cancer.

The extent of ADP-ribosylation in rectal cancer was compared to that of the corresponding normal rectal tissue. Twenty rectal tissue fragments were collected during surgery from patients diagnosed as having rectal cancer on the basis of pathology results. The levels of ADP-ribosylation in rectum cancer tissue samples (95.9 +/- 22.1 nmol/ml) was significantly higher than in normal tissues (11.4 +/- 4 nmol/ml). The level of NAD+ glycohydrolase and ADP-ribosyl cyclase activities in rectal cancer and normal tissue samples were measured. Cancer tissues had significantly higher NAD+ glycohydrolase and ADP-ribosyl cyclase activities than the control tissues (43.3 +/- 9.1 vs 29.2 +/- 5.2 and 6.2 +/- 1.6 vs 1.6 +/- 0.4 nmol mg(-1) min(-1)). Approximately 75% of the NAD+ concentration was consumed as substrate in rectal cancer, with changes in NAD+/ADP-ribose metabolism being observed. When [14C]-ADP-ribosylated tissue samples were subjected to SDS-PAGE, autoradiographic analysis revealed that several proteins were ADP-ribosylated in rectum tissue. Notably, the radiolabeling of a 113-kDa protein was remarkably greater than that in control tissues. Poly(ADP)-ribosylation of the 113-kDa protein in rectum cancer tissues might be enhanced with its proliferative activity, and poly(ADP)-ribosylation of the same protein in rectum cancer patients might be an indicator of tumor diagnosis.

ADP-ribosyl Cyclase↗

Antibiotic-associated diarrhea in a Turkish outpatient population: investigation of 288 cases.

Oral antibiotics are often prescribed, especially for respiratory tract infections in the community. The widespread use of broad-spectrum antibiotics causes an increased incidence of antibiotic-associated diarrhea (AAD). Although AAD has been studied in hospitalized patients, there is little available information concerning the characteristics of AAD in outpatient populations. The aim of this study was to investigate the clinical and laboratory findings of adult patients with community-acquired AAD. Between June 1998 and December 2003, the clinical reports of 288 patients were retrospectively reviewed. We observed that the duration between the start of antibiotic treatment and onset of symptoms was 7 days in most of the patients (86%), and the mean time was 9+/-1.0 days. The diarrhea was self-limited in all cases and mean duration of symptoms was 3 (+/-1.0) days (1-7 days). The most common symptoms were abdominal discomfort and tenesmus (61.1%), while elevated WBC counts and fever were detected rarely. We were able to perform microbiologic investigations in only 88 patients because of the financial problems. Of the 88 stool specimens tested, none of them were positive for pathogenic bacterial growth or toxin A production.

Administration, Oral↗

Enzyme-to-enzyme channelling in the early steps of glycolysis in rat pancreatic islets.

The metabolism of D-glucose displays anomeric specificity in rat pancreatic islets. The aim of the present report is to investigate whether such a situation implies enzyme-to-enzyme tunnelling of metabolites in the early steps of glycolysis. For such a purpose, the modelling of alpha- and beta-D-glucose catabolism, itself based on available information concerning both the utilisation of these two anomers and the intrinsic properties of phosphoglucoisomerase, was first examined. According to a theoretical model with enzyme-to-enzyme channelling, the generation of 3HOH from D-[2-3H]glucose should be higher in islets exposed to beta-D-glucose rather than alpha-D-glucose, whilst the opposite situation should prevail in the case of D-[5-3H]glucose conversion to 3HOH. Experimental data collected in rat islets incubated for 60 min at 4 degrees C in the presence of either alpha- or beta-D-glucose mixed with tracer amounts of either alpha- or beta-D-[2- 3H]glucose and alpha- or beta-D-[5-3H]glucose indicate that the beta/alpha ratio for D-[2-3H]glucose conversion to 3HOH is indeed higher than the beta/alpha ratio for D-[5-3H]glucose conversion to 3HOH. These findings are consistent with the postulated enzyme-to-enzyme tunnelling of glycolytic intermediates between hexokinase isoenzyme(s), phosphoglucoisomerase and, possibly, phosphofructokinase.

Animals↗

Metabolism of tritiated D-glucose anomers in rat erythrocytes.

It was recently proposed that alpha-D-glucose 6-phosphate may undergo enzyme-to-enzyme channelling between glucokinase and phosphoglucoisomerase in rat pancreatic islets. The present study aims at exploring whether a different situation prevails in cells deprived of glucokinase, namely in erythrocytes. At anomeric equilibrium, the ratio between D-[2-3H]glucose and D-[5-3H]glucose conversion to 3HOH was lower in rat erythrocytes incubated for 60 min at 4 degrees C in the presence of 2.8 mM, rather than 8.3 mM, D-glucose. This coincided with both a greater relative increase in beta-D-[5-3H]glucose, as compared to alpha-D-[5-3H]glucose, conversion to 3HOH and an increase in the beta/alpha ratio for 3HOH generation from D-[5-3H]glucose in response to an increase in the anomeric concentration from 2.8 to 8.3 mM, the suppression of the difference between the beta/alpha ratios for 3HOH generation from D-[2-3H]glucose and D-[5-3H]glucose in the erythrocytes incubated at 8.3 mM, as distinct from 2.8 mM, alpha- and beta-D-glucose, and a [2-3H]/[5-3H] ratio for 3HOH generation lower than unity in erythrocytes exposed to alpha-D-glucose but not significantly different from unity in the presence of beta-D-glucose. These findings emphasize the relevance of alpha-D-glucose 6-phosphate channelling between hexokinase and phosphoglucoisomerase as a determinant of the difference between D-[2-3H]glucose and D-[5-3H]glucose conversion to 3HOH, and reveal that the regulation of such a tunnelling process by the concentration of the D-glucose represents, in rat erythrocytes, a mirror image of that observed in rat pancreatic islets. The regulation of this process thus tightly depends on the identity of the hexokinase enzyme mainly responsible for the phosphorylation of D-glucose in distinct cell types.

Animals↗

Metabolism of D-glucose anomers in rat pancreatic islets exposed to equilibrated D-glucose.

This study aims at establishing the contribution of alpha- and beta-D-glucose to the total generation of (3)HOH by rat pancreatic islets exposed to D-[2 - (3)H]glucose or D-[5 - (3)H] glucose at anomeric equilibrium. The islets were incubated for 60 min at 4 degrees C in the presence of equilibrated D-glucose (2.8 and 8.3 mM) mixed with tracer amounts of either alpha- or beta-D-glucose labelled with tritium on either the C (2) or C (5) of the hexose. Relative to their respective concentrations, (3)HOH generation from the anomers labelled with tritium on the C (2) or C (5) of the hexose provided beta/alpha ratios comparable to those previously found at both 2.8 and 8.3 mM, when the islets were exposed to each anomer separately. The relative contributions of each anomer to the total generation of (3)HOH was also close to the theoretical values derived from mathematical models for the catabolism of D-glucose at anomeric equilibrium in rat islets at both 2.8 and 8.3 mM and in the case of both D-[2 - (3)H]glucose and D-[5 - (3)H]glucose. Thus, even in islets exposed to D-glucose at anomeric equilibrium, the metabolic fate of alpha-D-glucose differs vastly from that of beta-D-glucose, the enzyme-to-enzyme channelling between hexokinase isoenzymes, especially glucokinase, and phosphoglucoisomerase being restricted to alpha-D-glucose 6-phosphate.

Animals↗

Labelling of lipids by D-[1-14C]glucose, D-[6-14C] glucose and D-[3-3H]glucose in pancreatic islets from normal and GK rats.

In pancreatic islets prepared from either normal or GK rats and incubated at either low (2.8 mM) or high (16.7 mM) D-glucose concentration, the labelling of both lipids and their glycerol moiety is higher in the presence of D-[1-14C]glucose than D-[6-14C]glucose. The rise in D-glucose concentration augments the labelling of lipids, the paired 14C/3H ratio found in islets exposed to both D-[1-14C]glucose or D-[6-14C]glucose and D-[3-3H]glucose being even slightly higher at 16.7 mM D-glucose than that found, under otherwise identical conditions, at 2.8 mM D-glucose. Such a paired ratio exceeds unity in islets exposed to D-[1-14C]glucose. The labelling of islet lipids by D-[6-14C]glucose is about 30 times lower than the generation of acidic metabolites from the same tracer. These findings indicate (i) that the labelling of islet lipids accounts for only a minor fraction of D-glucose catabolism in pancreatic islets, (ii) a greater escape to L-glycerol-3-phosphate of glycerone-3-phosphate generated from the C1-C2-C3 moiety of D-glucose than D-glyceraldehyde-3-phosphate produced from the C4-C5-C6 moiety of the hexose, (iii) that only a limited amount of [3-3H]glycerone 3-phosphate generated from D-[3-3H]glucose is detritiated at the triose phosphate isomerase level before being converted to L-glycerol-3-phosphate, and (iv) that a rise in D-glucose concentration results in an increased labelling of islet lipids, this phenomenon being somewhat more pronounced in the case of D-[1-14C]glucose or D-[6-14C]glucose rather than D-[3-3H]glucose.

Animals↗

Underestimation of D-glucose utilisation as judged from the conversion of D-[3-(3)H]glucose to (3)HOH.

AIMS/HYPOTHESIS: The conversion of D-[3-(3)H]glucose to (3) HOH is currently measured to assess D-glucose utilisation. The validity of such a procedure was re-evaluated. METHODS: The conversion of D-[3-(3)H]glucose and D-[5-(3)H]glucose to (3) HOH was measured in rat pancreatic islets, parotid cells and erythrocytes. The tritiation of lipids were also examined in islets exposed to D-[3-(3)H]glucose or D-[5-(3)H]glucose. RESULTS: In rat pancreatic islets and parotid cells, but not in rat erythrocytes, the generation of (3) HOH from D-[3-(3)H]glucose underestimates the rate of D-glucose utilisation, this being apparently attributable to a partial escape from detritiation of [1-(3)H]glycerone-3-phosphate. Such an escape phenomenon resulted in a higher tritiation of lipids in pancreatic islets exposed to D-[3-(3)H]glucose, rather than D-[5-(3)H]glucose. Its relative extent was affected by a number of environmental factors such as the cell type under consideration, the metabolic status of the animals, and the extracellular concentration of D-glucose. CONCLUSION/INTERPRETATION: These findings impose a reservation on the use of D-[3-(3)H]glucose conversion to (3)HOH as a tool to assess the utilisation of the hexose in some cell types.

Amino Acids↗

Renal hemodynamic effects of L-NAME during postnatal maturation in conscious lambs.

The purpose of the present study was to investigate the effects of the L-arginine analogue, NG-nitro-L-arginine methyl ester, L-NAME, in modulating renal hemodynamics during postnatal maturation in conscious chronically instrumented lambs. To this end, renal hemodynamic responses to intravenous injection of 10, 20, and 40 mg/kg L-NAME, as well as its inactive enantiomer D-NAME, were measured for 4 h in conscious lambs approximately 1 week (n=10), 3 weeks (n=12), and 6 weeks (n=14) of age. Administration of L-NAME was associated with an increase in renal vascular resistance (RVR) leading to a decrease in renal blood flow. One-week-old lambs were more sensitive to the effects of L-NAME, a marked increase in RVR occurring after the smallest dose administered at 1 week but not at 3 and 6 weeks of age. Renal hemodynamic effects of L-NAME as well as the duration of the responses were also age dependent, such that changes in RVR were greatest and most prolonged in 1-week-old lambs. In addition, a smaller dose of L-NAME was required to attenuate acetylcholine-induced renal vasodilation in lambs aged 1 week compared with older animals. Our data provide new evidence to support the premise that endogenously produced nitric oxide plays a predominant role in regulating renal vascular tone early in life.

Aging↗

Nitric oxide modulates arterial baroreflex control of heart rate in conscious lambs in an age-dependent manner.

Experiments were carried out in conscious chronically instrumented lambs aged 1 (n = 6) and 6 wk (n = 5) to evaluate the arterial baroreflex control of heart rate (HR) during postnatal maturation and to investigate any modulatory role of endogenously produced nitric oxide (NO). Before and after intravenous administration of 20 mg/kg of the L-arginine analog N(G)-nitro-L-arginine methyl ester (L-NAME), the arterial baroreflex was assessed by measuring HR responses to increases and decreases in systolic arterial pressure achieved by intravenous administration of phenylephrine and sodium nitroprusside. The HR range over which the baroreflex operates and minimum HR as well as maximum gain were greater at 1 than at 6 wk of age. These age differences were abolished in the presence of L-NAME, which decreased the HR range and gain of the arterial baroreflex control of HR at 1 but not at 6 wk of age. These data provide new information that age-dependent effects of the arterial baroreflex appear to result from effects of endogenously produced NO.

Age Factors↗

D-mannoheptulose phosphorylation by hexokinase isoenzymes.

D-mannoheptulose is a specific inhibitor of D-glucose phosphorylation by hexokinase isoenzymes. In the present study, the phosphorylation of this heptose was investigated by either a spectrophotometric or radioisotopic procedure. Using yeast hexokinase, the phosphorylation of 25 mM D-mannoheptulose only represented 0.02% of that of 5 mM D-glucose. Such a percentage was increased to 3.93% in the case of bovine heart hexokinase. In the latter case, the Km for D-mannoheptulose was close to 0.2 mM and both D-glucose (0.1-1.0 mM) and D-glucose 6-phosphate (also 0.1-1.0 mM) inhibited the phosphorylation of the heptose (0.03-0.60 mM). Human B-cell glucokinase also catalyzed the phosphorylation of D-mannoheptulose (0.1 mM), which was now increased in a bell-shaped manner by D-glucose (1.0-20 mM). Likewise, rat parotid gland, liver and pancreatic islet homogenates catalyzed the phosphorylation of D-[3H]mannoheptulose. The results obtained in these three tissues differed from one another by their absolute values (per mg wet wt.), relative values (by reference to the phosphorylation rate of 10 mM D-glucose), and sensitivity to inhibition by D-glucose (10 mM).

Amino Acid Substitution↗

Uptake of 1-deoxy-1-[125I]iodo-D-mannoheptulose by different cell types: in vitro and in vivo experiments.

D-mannoheptulose was recently proposed as a tool to label preferentially insulin-producing cells in the pancreatic gland in the perspective of the non-invasive imaging of the endocrine pancreas. In such a perspective, we have now synthesized 1-deoxy-1-[125I]iodo-D-mannoheptulose ([125I]MH) and examined its uptake by different rat cell types. No phosphorylation of [125I]MH by bovine heart hexokinase could be detected. The apparent distribution space of [125I]MH largely exceeded that of [U-14C]sucrose, considered as an extracellular marker, in erythrocytes, parotid cells, hepatocytes, pancreatic pieces and isolated pancreatic islets. Relative to the mean intracellular distribution space of 3HOH, that of [125I]MH was not significantly different in pancreatic pieces from either normal rats or streptozotocin-induced diabetic animals (STZ rats). In pancreatic islets, the uptake of [125I]MH was decreased at low temperature, but failed to be significantly affected by cytochalasin B. Sixty min after the intravenous injection of [125I]MH, the radioactive content of selected organs displayed the following hierarchy: muscle<pancreas<liver<parotid<kidney<plasma. In this respect, there was no obvious difference between control and STZ rats. Taken as a whole, these findings suggest that 1-deoxy-1-[125I]iodo-D-mannoheptulose does not display the same specificity towards GLUT2, as that previously documented in the case of D-[3H]- mannoheptulose.

Animals↗

Uptake of D-mannoheptulose by normal and tumoral pancreatic islet cells.

D-mannoheptulose was recently proposed as a possible tool to label preferentially insulin-producing cells in the pancreatic gland. In the present study, D-[3H]-mannoheptulose uptake by rat pancreatic islets or dispersed islet cells was found to represent a time-related and temperature-sensitive process inhibited by cytochalasin B. This mould metabolite also inhibited the efflux of D-[3H]-mannoheptulose from prelabelled islets. After 60 min incubation at 37 degrees C, the apparent intracellular distribution space of the tritiated heptose was close to or somewhat higher than that of D-[5-3H]glucose and close to 50% of the intracellular 3HOH space. It was further enhanced by D-glucose and a high concentration of 10 mM of D-mannoheptulose. The uptake of D-[3H]mannoheptulose was much lower however than that of D-[3H]mannoheptulose hexaacetate. As judged from the fate of D-mannoheptulose hexa[2-14C]acetate, the latter ester was efficiently hydrolyzed in the islet cells. The internalization of D-[3H]mannoheptulose (or its ester) coincided with the generation of tritiated acidic metabolites, reflecting phosphorylation of the heptose. The situation found in normal islet cells sharply differed from that found in tumoral islet cells of either the RINm5F or INS-1 line, in which the apparent distribution space of D-[3H]mannoheptulose represented only about 3 and 9%, respectively, of the intracellular 3HOH space. These results indicate that the entry of D-mannoheptulose into islet cells represents a carrier-mediated process, possibly mediated at the intervention of GLUT2 and, hence, provide further support to the possible use of a suitable D-mannoheptulose analog as a tool for the preferential labelling of insulin-producing cells in the pancreatic gland.

Animals↗

Uptake of D-mannoheptulose by rat erythrocytes, hepatocytes and parotid cells.

D-[3H]mannoheptulose (or D-[1-14C] mannoheptulose) net uptake was measured in rat erythrocytes, parotid cells and hepatocytes. In the erythrocytes and parotid cells, the intracellular distribution space of the heptose (0.1 mM) represented only about 1 and 13%, respectively, of the intracellular 3HOH space. In hepatocytes, however, it amounted to approximately 45% of the intracellular 3HOH space. In all cases, the apparent distribution space of D-[3H]mannoheptulose hexaacetate largely exceeded that of unesterified D-[3H]mannoheptulose. Relative to the intracellular water space, the generation of acidic metabolites (expressed as an apparent distribution space) from radioactive D-mannoheptulose was one order of magnitude lower in parotid cells (< or = 3%) than in hepatocytes (> or = 20%). These findings are compatible with the hypothesis that D-mannoheptulose is transported into cells mainly, if not exclusively, at the intervention of GLUT2.

Animals↗